Production of mono and dichlor isomers of diphenyl



Patented Mar. 20, 1934 PATENT? oFFi-c EC:

1,551,5771. T a PRODUCTION or'A MoNo nicmton ISOMERS F DIBHENYL John E. Malo wan .Annistong Ala., assignor to Swann Research, Incorporated, a. corporation of Alabama.

N Drawing;"ap licationsepteinbertfl932, SerialNo.631;754 i m Claims. "(01. 260-161) invention relates to the production of mono and dichloro isomersof diphenyl by chlorinl ation. One objectof this invention is the pro;

vision of a process by which increased yieldsof 1 the monochlor and dichlordiphenyls maybe obtained. t Another object is the provision of a process by which diphenyl is chlorinated in asolvent havinga boiling point above that of the monochlorodiphenyl isomers, inorder to facilitate sepa 3 p 0 ration thereof, Other objects and advantages will become apparent as the disclosure proceeds.

It is already known that diphenyl oanbe chlorinated for the production of the monoehlor isomers, either by passinglchlorinedirectly into ,15 theinoltenhydrocarbon or by dissolving it first in a solvent such asbenzene, toluene or the liquid rnono anddihalogenated derivatives of benz neor toluene, and then chlorinating such solution. In the first-mentioned known method, the yields of -the monochlor diphenyls obtained are comparatively low; due to theformation of large a quantities of highertchlorinated diphenyls as well t as toythefact that relativelylarge fiuantities of the original-diphenyl areflnot chlorinated. v r i Theobjections to thesecond known method ar in general similarto those above mentioned and in addition from a commercial standpoint it is objectionable because it isnecessary to distill a largequantity of the volatileisolvent before the v ".330 monochlordiphenyls canbe distilled.

method of obtaining the monochlor; andjthe dichlorisor nerslof diphe iyl be devised. I TheLZ-and -chlordiphenyl are useful as a starting poihtl for the i manufacture of the corresponding hydroxy i or} amino con pounds. flhe ndichlorlflisomer of diphenyl which is of greatest interest is the 14-4;-

dichlordiphenyl which is useful as a a starting ma- I terial fqr the manufactureof benzidina hat diphenl ma'y b I have now discovered chlorinated diphenyl and high yields of themono chlor or dichlor isomer obtained without further chlorinat lg such solvent. I have also found that a not linconsiderable saving results upon subsee rquent distillation "of the monochlor i isomers because gof thefactthat such isomers iar e readily .distilledrfrom the chlorination product ata boildiphenyl which hasbeenrused as a solvent. 7 y The higher 'chlorinateddiphenyls which are diphenyl during chlorination, are those chlorinated diphenyls having two or more chlorine atoms It is partieularly desirable that a more eiiicient chlorinated if first: dissolved ina liquid higher a Anexample of such use will be ingpoint below; that of thehigher chlorinated liquidliand which aroused as a solventlforthe Emmpzer v Chlorinate diphenyl by passing chlorinefgas into the a hydrocarbon above its melting point. Iron filings are added to the diphehyl to catalyze the chlorination reaction. After chlorination has started, the temperature of the diphenylmay1be reduced to 40 C. or lower by passing] eoldwater thru cooling coils submerged in thereacting I have found that if the temperaturelpbernainf-f tained somewhat above the freezing temperature of the reacting mass chlorination proceeds somewhatfslower, but agood yield of i l' -dichlordi' phenfvl may be obtained uponcooling, 0111mm tion is continued until a chlorine contentcin the neighborhood of 32 percent is reached, atwhich point the flow ofgas is interrupted and chlorination is complete. Upon cooling the reaction ture to 20 C. or lower, crystals of def -dichlordiphenyl separate out. "Ihesemaybe filteredfor otherwise separated from the motherliquor', and

represent in amount a yield of approximately 30% of the original diphenyl. The mother liquor after separation ofr the 4-4'Adichlordipheny1 has a specific gravity in the neighborhood of 1.259 at C./65 0;, and a freezing point considerably below 20?: C. This mother; liquor is suitable for useas asolvent medium for further chlorination of diphenyhas will hereinafter more fully appear.

Due to the low freezing point of the chlorinated diphenyl mothertliduor the solution made theretemperatures, for the production of which refrigcrating plants are required a i 1 a a 7 apparent from the following procedure 1 illustrating one method by which higher yields of 4-4-dichlordiphenyl may beproduced:-

Example II :DiSlJll' one part of diphenyl micelt rts bt weight of the mother liquor chlorinate the the mother liquor. However, as the chlorination.

reaches the dichlor stage, crystals of 4-4-dichlordiphenyl begin to separate out. I tion of chlorination, the chlorinated product is cooled to 20 C. or below and the'separate'd crystals removed by filtration' o'r otherwise without removing appreciable mother liquor or other isomers.

added.

An example of the use of the above-mentioned mother liquor for the chlorination of diphenyl in theproduction of the monochlor isomers is'given in; the following:-

. Ewample III 1 products obtained will consist of: unchanged di- 1 phenyl, 2Q precent; monochlordiphenyls equivalent to 80% of the original diphenyl; higher chlo rinated diphenyls, none. The monochlordiphenyls comprise: 2-chlordiphenyls 62.5% and 4-chlcrdiphenyls 37.5%.

1 Some variation in the extent of chlorination is, of course permissible. If a greater amount of chlorine be introduced into the solution of Example'IILa somewhat larger amount of diphenyl will be chlorinated, but some dichlordiphenyls will be produced. If a lesser amount of chlorine be introduced, a larger amount of diphenyl remains unchlorinated. From the above examples it will be seen that myinvention provides a process for the chlorination of diphenyl by which a more uniform chlorination may be obtained than was hitherto possible, and which is not complicated by the distilla- .tion of volatile solvents, in which such chlorinations have hitherto been conducted. The separation of the desiredisomers can be effected in asimple and economical manner," as described. The separation of the 4-.4f-dichlor isomer is accomplished by crystallization, whereby it is obtained in a relatively pure state. The separation of the monochlor isomers is effected most conveniently by fractional distillation, sincethey boiLat a lower temperature than the solvent in which they have been chlorinated. They. may :also, ifdesired be separatedonefrom the other by fractional, distillation because of thediifer- 'ence in boiling point. The Z-chIordiphenyl boils at 26' 7-268 C.; the4j-chlordiphenyl boils at 282 C while the liquid chlorinated diphenyl suitable for use .as a solventboils above 293 C.

While I have described only three embodiments of my invention, it will be apparent to those skilled in the art that it is not so limited, but that it is susceptible of .variouschanges, and modifications without departing from the spirit thereof, and I desire that only'such limitations shallbe placed Upon comple- The yield of the 4-4 isomer will be in the neighborhood of 40 Percent Of dip hyh isomers of diphenyl, comprising dissolving diwhile in solution.

2. A process for the production of chlorine derivatives of diphenyl, comprising dissolving d1- phenyl in a liquid mixture of higher chlorinated diphenyls having a freezing point substantially below 20C. and then chlorinating said diphenyl while in solution.

3. 'A process for the production of monochlor phenyl in a liquid mixture of higher chlorinated diphenyls, chlorinating said diphenyl while in solution and then separating said monochlor isothere by fractional distillation.

4. A process for the production of monochlor isomers of diphenyl, comprising dissolving diphenyl in a liquid mixture of higherchlorinated diphenyls having a freezing point substantially below 20 C., chlorinating said dissolved diphenyl at a temperature below C. and separating said monochlor isomers by fractional distillation. 1

5; In a process for the production of chlorine derivatives of diphenyl, in which chlorine and diphenyl dissolved in a liquid mixture of higher chlorinated diphenyls are reacted to form chlorine substitution products thereof, the step of separating the 4-4-dichlor isomer by crystallization from said liquid mixture of higher chlorinated diphenyls by cooling the reaction product below 20". C. and removing said isomer from the mother liquor. y y

6. A process for the production of chlorine derivatives of diphenyl, comprising dissolving diphenyl in a liquid mixture of higher chlorinated derivatives of diphenyl having a freezing point substantially below 20 C., chlorinating said dissolved diphenyl, cooling the reaction product below 20 C. ad removing the crystalline 4-4- dichlordiphenyl derivative from the mother liquor.. I 7. In the process defined in claim 6, the steps of dissolving diphenyl in-the mother liquor from which crystals of 4-4'-dichlordiphenyl have been removed, in the proportion of one part of diphenyl to four parts of mother liquor and then chlorinating the solution to produce the monochlor isomers.

8. In the process defined in claim 6, the steps of dissolving diphenyl in the mother liquor from which crystals of 4-4'-dichlordiphenyl have been removed, and then chlorinating the solution at a temperature below 40 C. to produce the monochlor isomers.

9. A process for the production of chlorine derivatives of diphenyl comprising dissolving diphenyl in a liquid mixture of higher chlorinated diphenyls of approximately 1.259 specific gravity at /65 C., chlorinating the solution until sufiioient chlorine .has been combined with the dissolved diphenyl to form the dichlordiphenyl,

then cooling the product to crystallize the 4-4- dichlordiphenyl derivative, and separating the same from'the motherliquor. r

110; A process for the production of monochlor isomers of diphenyl, comprising dissolving diphenyl in a. liquid mixture of higher chlorinated diphenyls of approximately 1.259 specific gravity at 65 65 C., chlorinating the solution, and then 1 isomers from the solution by fractional distillaseparating the monochlor isomers from the solution by fractional distillation.

11. A process for the production of monochlor isomers of diphenyl, comprising dissolving diphenyl in a liquid mixture of higher chlorinated diphenyls of approximately 1.259 specific gravity 1 at /65 C., chlorinating diphenyl in the solution until approximately of the dissolved diphenyl has been chlorinated and then separating the unchanged diphenyl .and the monochlor isomers and a freezing point substantially below .a v 3 20 C., and then chlorinating the dissolved dip 'yl. a

14. Process for the production of 4-4-dichlorodiphenyl, comprising dissolving diphenyl in a liquid mixture of higher chlorinated diphenyls having a boiling point substantially higher than the monochlorodiphenyls and chlorinating said diphenyl to form the said dichlorodiphenyl.

15. Process for the production of 44'-dichlorodiphenyl comprising dissolving diphenyl in a liquid mixture of higher chlorinated diphenyls having a freezing point below 20 C. and then chlorinating said diphenyl to form the said,

dichlor isomer. 1

v 16. Process for the production of the monoehlor isomers of diphenylcornprising dissolving diphenylin a liquid mixture of higher chlorinated diphenyls having a boiling point above that of the monochlor isomers, chlorinating said dissolved diphenyl, and then separating said monochlor isomers from the higher chlorinated diphenyls bydistillation. i

JOHN E. MALOWAN. 

